Process of patching plywood



Jan. 2, 1951 P. F. sKooG PROCESS 0F PATCHING PLYwooD Filed Jan. 10, 1949 F. snode :Snoentor Gttornegs Patented Jan. 2, 1951 TED smsrfas .a-ram .optics il The present invention relates -to vprocess of patching plywood.

In f the past, there l has f not been a-satisfactory method for patching the face of=a-plywoodfsheet- By.plywood sheetis meantasheetwcomposedof l a-plurality-of layers of -wood whichjareheld together Aby -an adhesive and *which has at least onenface .layer o f thin veneersheet. Usually the `face sheets ofplywood are.patched before being Ylayed `on and bonded tothe 'corestock. However, it 'ften happens that lzl'efects appear in 'ther-face veneers of plywood. Further, work with the npresent process has vindicated"that -it may -cost lless .to patch the Veneer face sheet of fthe nishe'd f.plywood than vItopatch the veneer sheets "before -the'y `'are laye'dnto .plywood Further, -fthefproduct obtained by tlregpresent processf has a better appearance, as fthe. present patches do not show as readily as thoseofthe priorgart,whetherthepatch rwas applied to the vencen-before *laying Yup orafter' laying up.

vIn the prior art of patch'ng aplywodd sheet, the-area to beMpa-tched was routed outby the use of any suitable rotary or hand tools, a patch was shaped to1therouted=-=area `and secured in -the routed depression by means of an adhesive. In` the present "process, the 'area to be :patched is indented by applying to thaht'are'a amale die and forcingtlfie-die lintotheshetto form an indentation. This pressing -of the die into the sheet-compresses and distorts the material or bersof the sheet to formfftheindentation. A patch,1usually a piece of woodveneer conforming 1to1 theformed indentation -is placed: and :securedftherein by a suitable adhesive. The. patch is :preferably *of a thickness-slightly moreithan the depth of the indentation. During the setting of the adhesive, the sheet may be secured in a press. Following setting of the adhesive of the patch, the face of the patch may be sanded down to the surface of the sheet. In the nished product, the edges of the patch blend with the face sheet making the patch hardly noticeable. This is particularly true if the grain of the patch is arranged in line with the grain of the material around the patch.

Having in mind the defects of the prior art, it is among the important objects of this invention to provide: a process capable of rapid performance for the patching of plywood to hide and conceal surface defects and marred areas or to inlay pattern-forming elements in the face of plywood; a process of patching plywood in which the patch element can be inserted and made substantially invisible; a process in which a 2 patch receving 'indentation is formed fby Scompression and deformation of 'the `material `and :without `'invelying'l the removall 'ofi material from `the plywoodrorfrequiring:routing "or'fcutting of the 'Ssheet lof plywood; a process "capable` of performa'nc'e lwith simple equipment `and Eby relatively 'unskilled iabor, 'yet `resulting in the, production'fofihi'ghly satisfactory results; and-an improved 'patched "p13/"wood-as y1a new article of manufacture.

"Ihesteps ci* the process, and fthe;y product-are illustrated rin fthe faccomp'anyin'g drawing, in which:

lFigure fl his lla lse'ctional'fview .fof :thel indenting ieaiidplywoodfsheettofbe patched;

H'Figure 3- is -'a sectional f'view iof lthe indented sheetia'ndia patch Vto'be applied thereto;

Figure 14 :is 'a sectional 1View v`fof 'the patched sheet inva.pressforsetting the -adhesiveof the patch;

/igure'f lis a sectional viewillustrating the step 'f sanding the patch and Figureisa'perspectve view'of the finished product Awith; part of the patch broken away.

tInrFigure 11 fI'show a plywcodfsh'eet vI composedcf `a *core f2 formed of cross-band stock 'and facings'plires and-li; one of which'niay' have -a 'marred 7 area l"5 that y#is to be patched. The areal Inf-ray alsobefobjectionable'because it is stained lorhas a1kn'ot1or-the like that is to "be hidden.

fMy .process i is performed @by .placing the sheet l 'Torrl a .1 rm be'd e with thef-fa'rea-l 5 oriented f beneath the :fdi'e '7. aUnder "rcertain circumstanc'es I employ "ai-clamping frin'g 19 to :secure `the plywood tc the bed 6. The use of this clamping ring is desirable but not indispensable, and when it is used sufcient pressure is applied by means not shown to prevent outward bulging of the sheet while indenting is being conducted, or to prevent sh'ftng of the plywood before the die can be brought into operation. Such pressure should not be sufficient to mar the sheet about area 5. The die is likewise caused to descend and enter the plywood by suitable pressure means (not shown). but which may be hydraulic or cam-actuated, or of any other conventional nature.

As the die enters the plywood sheet, the face sheet l and the core stock 2 are forced and displaced downward and compressed and distorted to produce indentation 9 shown in Figure 3. The indentation has the shape of die 1.

The preferable form of patch is known in the field as boat-shaped in that it has the pointed ends and curved or double convex edges therebetween. This shape of patch is most hidden in the grain of the plywood face veneer but other shapes are equally applicable as then designs are being let into the plywood for ornamental purposes.

To form an indentation for a boat-shaped patch, the face l0 of the die is flat and pointed or boat-shaped. Other shapes are also used for the reasons stated above. The edges of the die are formed with a chamfer i I and are curved to the curvature of the boat-shaped patch. This chamfer may be straight or formed with an ogee cross-section. In the latter instance, the intersection of the charnfer and the face l 6 is convex, which merges with a concave portion, This shape for the chamfer reduces breakage of the bers of the sheet and, also, aids in blending the patch, when applied and sanded down, into the face Veneer of the plywood sheet.

Following formation of the indentation, the die and clamping ring are raised from the sheet and a preformed patch l2 of the configuration of the indentation, as shown in Figure 3, is readied for application to the indentation. An adhesive, not illustrated, such as is usual in the manufacture of plywood, is applied to the indentation and may also be applied to the faces of the patch. The patch is then placed in the indentation and the sheet placed in a press, as illustrated in Figure 4, for setting of the adhesive and for maintaining the patch in position and alignment with the indentation during the setting period. In Figure 4. there is shown the plywood sheet l, the patch I 2 inserted in the indentation, a press bed 6, and a pressing shoe I4 holding the sheet in compression on the press head 6. Depending on the nature of the adhesive used, heat may or may not be supplied to shoe i4. Usually, the patch is slightly thicker than the depression depth. This allows for a small amount of sanding of the patch before the sander drum l5, Figure 5, contacts the surrounding face veneer 4. This sanding step is i.

the final step in blending the patch into the sheet.

In the prior art processes of patching a plywood sheet, when the patch area is routed out, the fibers of the wood are rather sharply cut along the surface edge. The result is that the juncture line of the patch and surface veneer is clearly defined and, hence, objectionable. In the present process, the surface fibers of the face veneer around area 5 are bent downward and under the patch. The sanding of the patch feathers the edge bers of the tapered patch so that the juncture line of patch and sheet is well hidden.

'Ihis blending of the patch into the surface of the sheet is diicult to show clearly in a drawing, but an attempt has been made in Figure 6 to illustrate such. Normally, the feathered edge of the patch is wavy and such blends well with the grain of the veneer face 4, as well as that of the patch. Of course, where ornamental inlaying is being done, as with strongly contrasting Woods, the indenting and patching can be done with more abrupt angles and sharper denition will result.

Having thus described my invention, I claim:

1. The process of patching a plywood sheet composed of a plurality of veneers in which an outward veneer has a visible defect, comprising: bending inward the material forming the area of said visible defect and compressing the cellular structure or said material without removing any of the material thereof so as to form an indentation having a substantially flat bottom and sloping side walls; then positioning in said indentation and securing with adhesive a patch having a similar shape to said indentation and having a slightly larger size than said indentation with the graining running from end to end thereof and with the cellular structure in its normal form; and then sanding the surface of said veneer to remove the portions of said patch extending beyond the surface of said veneer.

2. The process of 'patching a plywood sheet composed of a plurality of veneers in which an outward veneer has a visible defect, comprising: distorting inward the material forming the area of said visible defect and compressing the cellum lar structure of said material without removing any of the material thereof so as to form an in dentation having sloping side walls; then positioning in said indentation and securing with adhesive a patch having a similar shape to said indentation with the graining running from end to end thereof and with the cellular structure in its normal form.

PER F. SKOOG.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS' Number Name Date 1,005,546 Hobart Oct. 10, 1911 1,911,374 Loetscher May 30, 1933 1,969,766 Nash Feb. 5, 1935 2,175,654 Alenius Oct. 10, 1939 2,263,536 Dike Nov. 18, 1941 2,447,609 Breece Aug. 24, 1948 

